JP6107669B2 - Abrasive recycling method - Google Patents

Description

  The present invention relates to an abrasive recycling method for recovering a used abrasive from a used abrasive slurry and reusing it as a recycled abrasive.

  Conventionally, fine particles with high hardness represented by diamond, boron nitride, silicon carbide, alumina, alumina zirconia, zirconium oxide, cerium oxide, etc. have been used as polishing materials for precision polishing of optical glass and quartz oscillators in the finishing process. Has been.

  In general, some of the main constituent elements of abrasives are obtained from minerals that are not produced in Japan, and some of them are resources that depend on imports and are expensive in terms of material prices.

  Since these abrasives are fine particles with high hardness, they are important resources that are used in large quantities as optical abrasives for electronic parts such as optical lenses, semiconductor silicon substrates, and glass plates for liquid crystal screens. It is one of the resources that are strongly desired to use. In addition, the polishing material for optical polishing may contain transition metal elements such as sodium salts and chromium salts, and fine particles of rare earth elements such as yttrium and decyprosium, with each of the above compounds as a main component. Disposal is strongly prohibited by the environment. For this reason, development of a processing technique for making the waste liquid used for polishing pollution-free is strongly desired. Therefore, regarding the optical abrasive waste liquid containing the used abrasive, it is an important problem to recycle resources or to deal with pollution-free.

  Generally, wastewater containing suspended fine particles generated in various industrial fields is treated by aggregating and separating suspended fine particles using a neutralizing agent, inorganic flocculant, polymer flocculant, etc., and then the treated water is discharged. However, at present, the coagulated and separated sludge is disposed of by incineration or other means.

  In addition, these abrasives are usually used in a large amount in the polishing step, and the components to be polished, such as optical glass scraps, coexist in the waste liquid, but usually the abrasive and the components to be polished are included. Because it is difficult to separate efficiently, as described above, the abrasive waste liquid is often discarded after use, which is also a problem in terms of environmental burden and disposal cost. Have

  Therefore, in recent years, it has become an important problem to efficiently recover and reuse the main constituent elements of the abrasive to save resources of elements with high rare values.

  With regard to the method for recovering the abrasive component, for example, an electrolyte substance is added to the used abrasive, the abrasive is coagulated and precipitated, the component derived from the polished substrate (the component to be polished) is dissolved, and solid-liquid separation is performed. (For example, refer to Patent Document 1). In the method described in Patent Document 1, alkali metal hydroxide, alkali metal carbonate, alkali metal salt, and ammonium salt are used as the electrolyte substance.

  Further, a method is disclosed in which a fine abrasive is recovered by mixing sodium hydroxide and potassium hydroxide solution with a used abrasive and sieving the solid by solid-liquid separation (for example, , See Patent Document 2). Furthermore, a method is disclosed in which a rare earth or a rare metal is dissolved by adding sulfuric acid to a used abrasive and subjected to heat treatment, and separated and removed from aggregates such as silica in the slurry (for example, patents). Reference 3).

  In addition, as a method for recovering the colloidal silica-based abrasive, agglomeration treatment is performed on a CMP (Chemical Mechanical Polishing) waste liquid by adding an alkali in the presence of magnesium ions and adjusting the pH value to 10 or more. (See, for example, Patent Document 4). Further, Non-Patent Document 1 provides a review on the above-described metal recovery technology.

  However, in the methods disclosed in Patent Documents 1 to 4, since the purity of the recovered abrasive is not sufficient, the recovered abrasive is not suitable for high-precision polishing.

  Further, in the method of Patent Document 4 described above, when a polishing material containing cerium oxide as a main component and glass or the like containing silicon as a main component is to be polished, the abrasive slurry containing a used abrasive is used. When an additive such as magnesium chloride is added under a condition where the pH is 10 or more, the abrasive component is aggregated together with glass or the like, leading to a decrease in the purity of the obtained recycled abrasive. The reason is that, when the pH is 10 or more, the cohesiveness of a component derived from a polishing target mainly composed of silicon (glass or the like) is increased, and the addition of an additive causes easier aggregation than the abrasive component. it is conceivable that.

  Patent Document 5 describes a method for producing a regenerated cerium oxide abrasive by regenerating secondary particles of cerium oxide, which is an abrasive, by freezing a used recovery liquid and then removing water. However, the method described in Patent Document 5 requires a large facility for freezing and the initial investment becomes very large.

Japanese Patent Laid-Open No. 06-254664 JP-A-11-90825 Japanese Patent Application Laid-Open No. 11-50168 JP 2000-254659 A JP 2010-214515 A

Metal Resources Report 45 pages 2012.11.

  The present invention has been made in view of the above-mentioned problems, and the problem to be solved is to recover the abrasive from the used abrasive slurry by an efficient method, and then recycle the high purity by a simple method. It is providing the abrasive | polishing material reproduction | regeneration method which can obtain material.

As a result of intensive studies in view of the above problems, the present inventors have used a specific abrasive as an abrasive as a polishing material recycling method for regenerating an abrasive from a used abrasive slurry, and used polishing. A slurry recovery step A for recovering an abrasive slurry containing a material and a pH adjusting agent are added, and an alkaline earth metal salt is added as an inorganic salt in a state in which the non-abrasive material is not aggregated to aggregate the abrasive, and the mother liquor From the used abrasive material, the separation and concentration process B for separating and concentrating the abrasive material, and the abrasive material recycling method for recovering the abrasive material through the abrasive material collecting process C for recovering the separated and concentrated abrasive material, As soon as the present invention has been found, it has been found that an abrasive recycling method can be realized in which an abrasive can be recovered by an efficient method and then a high-purity recycled abrasive can be obtained by a simple method.

  That is, the above problem of the present invention is solved by the following means.

  1. A polishing material regeneration method for regenerating an abrasive contained in the abrasive slurry from a used abrasive slurry, wherein the abrasive is at least one abrasive selected from the following abrasive group, and A method for regenerating an abrasive material comprising regenerating the abrasive material through steps A to C.

Step A: Slurry recovery step A for recovering the abrasive slurry discharged from the polishing machine,
Step B: To the recovered abrasive slurry , an alkaline earth metal salt is added as an inorganic salt in a state in which no pH adjusting agent is added and a non-abrasive is not aggregated to aggregate the abrasive, and the abrasive Separating and concentrating step B, in which the product is separated from the mother liquor and concentrated.
Step C: Abrasive recovery step C for recovering the separated and concentrated abrasive.

Abrasive group: diamond, boron nitride, Alumina, alumina zirconia and zirconium oxide.

  2. 2. The abrasive recycling method according to claim 1, further comprising a particle diameter control process D (process D) for adjusting a particle diameter of the recovered abrasive after the abrasive recovery process C. 3.

  3. In the separation / concentration step B, the separation / concentration process is performed under the condition that the pH value of the mother liquor in terms of 25 ° C. is less than 10.0.

  4). 4. The abrasive according to claim 1, wherein the slurry recovery step A recovers the abrasive slurry 1 containing cleaning water and the used abrasive slurry 2. 5. Playback method.

  5. 5. The abrasive recycling method according to claim 4, wherein the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A are mixed and then processed in the separation and concentration step B and the recovery step C. .

  6). 5. The abrasive material regeneration according to claim 4, wherein the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A are independently processed in the separation and concentration step B and the recovery step C, respectively. Method.

  7). The method for regenerating an abrasive according to any one of Items 1 to 6, wherein the alkaline earth metal salt used in the separation and concentration step B is a magnesium salt.

  8). The method for recovering an abrasive according to any one of items 1 to 7, wherein the method for recovering the abrasive in the abrasive recovery step C is a decantation separation method by natural sedimentation.

  9. In the particle size control step D, after adding a dispersant to the recovered abrasive solution, the particle size of the recycled abrasive is controlled by dispersing using an ultrasonic disperser or a bead mill type disperser. The method for regenerating an abrasive according to item 2.

  10. 10. The abrasive recycling method according to item 9, wherein the disperser used in the particle diameter control step D is an ultrasonic disperser.

  11. 11. The method for regenerating an abrasive material according to item 9 or 10, wherein the dispersant is a polycarboxylic acid polymer dispersant.

  By the above-mentioned means of the present invention, there can be provided an abrasive recycling method capable of recovering an abrasive from an used abrasive slurry by an efficient method and then obtaining a high-purity recycled abrasive by a simple method. .

  The reasons why the above effects are exhibited in the present invention are not clear, but are presumed as follows.

  The feature of the effect of the present invention is that the technology for recovering only the abrasive at a high concentration from the used abrasive slurry not only recovers the abrasive but also increases the purity at the time of recovery, Regeneration after collection is easy.

  The technical idea is presumed to be due to the specific compatibility between the abrasive and the inorganic salt.

  It is a common practice to add a flocculant having a large specific gravity to a used abrasive and separate it as a solid component, and then refine and recycle the abrasive. At that time, the abrasive recovered as a solid component includes a glass component, for example, silicon dioxide particles as an object to be polished by glass polishing. In order to separate this glass component, various purification steps are further required.

  In response to the above problem, in the abrasive recycling method of the present invention, the inorganic salt (alkaline earth metal salt) selectively aggregates only with the abrasive, and the glass component which is a non-abrasive hardly aggregates. Since it is present in the mother liquor, only the abrasive can be efficiently separated with high purity, and the simplification of the process that does not require a subsequent purification step can be realized.

  In the present invention, as the pH of the mother liquor containing the used abrasive slurry, a constant pH condition, that is, addition of an inorganic salt, is added without adding a pH adjusting agent until the aggregate is separated after the inorganic salt is added. It is preferable to maintain the pH below that of the hour. The pH at the time of inorganic salt addition here means the pH immediately after the addition of the inorganic salt is completed in the separation and concentration step B.

  Generally, in order to dissolve the glass component contained in the waste liquid, a means for increasing the pH of the waste liquid is taken. However, in the present invention, the glass component does not aggregate by using an inorganic salt, for example, a magnesium salt. Does not require pH adjustment.

  In addition, a part of the inorganic salt used for recovery is adsorbed to the abrasive particles and remains in the recycled abrasive, but this inorganic salt has a specific bond to some abrasives. Therefore, it has been found that the subsequent use as an abrasive also has an effect of suppressing the formation of fine particles of the abrasive.

The schematic diagram which shows an example of the basic process flow of the abrasives reproduction | regeneration method of this invention Schematic showing an example of the flow of separation and concentration step B and abrasive recovery step C in the abrasive recycling method of the present invention Schematic diagram showing an example of the processing flow of the particle size control step D using an ultrasonic disperser

  The abrasive recycling method of the present invention is an abrasive recycling method for recycling an abrasive contained in an abrasive slurry from a used abrasive slurry, and the abrasive is at least selected from the following abrasive group It is a kind of abrasive, and the abrasive is regenerated through the following steps A to C.

  Step A: Slurry recovery step A for recovering the abrasive slurry discharged from the polishing machine.

Step B: To the recovered abrasive slurry , an alkaline earth metal salt is added as an inorganic salt in a state in which no pH adjusting agent is added and a non-abrasive is not aggregated to aggregate the abrasive, and the abrasive Separation and concentration step B, in which the product is separated from the mother liquor and concentrated.

  Step C: Abrasive recovery step C for recovering the separated and concentrated abrasive.

Abrasive group: diamond, boron nitride, Alumina, alumina zirconia and zirconium oxide.

  This feature is a technical feature common to the inventions according to claims 1 to 11.

  As an embodiment of the present invention, the abrasive material recycling method of the present invention preferably further includes a particle size control step D for adjusting the particle size of the recovered abrasive material after the abrasive material recovery step C. . In the separation and concentration step B, the abrasive can be separated and concentrated more efficiently and reliably than the mother liquor by performing separation and concentration under the condition that the pH value of the mother liquor in terms of 25 ° C. is less than 10.0. . Moreover, it is preferable that the said slurry collection | recovery process A collect | recovers the abrasive slurry 1 and the used abrasive slurry 2 containing washing water. Further, in the abrasive recycling method of the present invention, the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A are mixed to prepare a mother liquor, and then the separation and concentration step B and the recovery step C are used. It is preferable that the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A are independently processed in the separation and concentration step B and the recovery step C, respectively. The alkaline earth metal salt used in the separation and concentration step B is preferably a magnesium salt. Moreover, it is preferable that the method of recovering the abrasive in the abrasive recovery step C is a decantation separation method by natural sedimentation.

  Furthermore, in the abrasive material regeneration method of the present invention, the particle size control step D is performed by adding a dispersant to the recovered abrasive solution and then dispersing it using an ultrasonic disperser or a bead mill type disperser. It is preferable to control the particle diameter of the recycled abrasive. Further, in the abrasive material regeneration method of the present invention, the disperser used in the particle size control step D is an ultrasonic disperser, and the dispersant is a polycarboxylic acid polymer dispersant. This is preferable because the effects of the present invention are more manifested.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, "-" shown in this invention is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

《Abrasive recycling method》
First, the process flow of the whole abrasive | polishing material reproduction | regenerating method of this embodiment is demonstrated using figures.

  FIG. 1 is a schematic diagram showing an example of a basic process flow of the abrasive material recycling method of the present embodiment.

In the polishing step shown in FIG. 1, the polishing apparatus 1 has a polishing surface plate 2 to which a polishing cloth K composed of a nonwoven fabric, a synthetic resin foam, a synthetic leather and the like is attached. Is rotatable. At the time of the polishing operation, the polishing surface plate 2 is rotated while the object to be polished (for example, optical glass or the like) 3 is pressed against the polishing surface plate 2 with a predetermined pressing force N using the holder H. At the same time, the abrasive liquid 4 (abrasive slurry 2) is supplied from the slurry nozzle 5 via the pump P. The used abrasive liquid 4 is stored in the slurry tank T ₁ through the flow path 6 and repeatedly circulates between the polishing apparatus 1 and the slurry tank T ₁ .

Further, the cleaning water 7 for cleaning the polishing apparatus 1 is stored in the cleaning water storage tank T ₂ , and cleaning is performed by spraying the polishing portion from the cleaning water jet nozzle 8 to include a cleaning liquid 10 ( The abrasive slurry 1) is stored in the cleaning liquid storage tank T ₃ through the flow path 9 via the pump. This washing liquid storage tank T ₃ is a tank for storing washing water after being used for washing (rinsing), and is constantly stirred by a stirring blade in order to prevent precipitation and aggregation.

Stored in the slurry tank T ₁ generated in the polishing step, the circulating abrasive liquid 4 was used (abrasive slurry 2), the cleaning liquid 10 stored in the cleaning liquid storage tank T ₃ (abrasive slurry 1) Both of them are in a state of containing, together with the abrasive particles, a non-abrasive material scraped off from the workpiece (eg, glass) 3 polished in the polishing step 1.

  Next, the abrasive liquid 4 (the abrasive slurry 2) and the cleaning liquid 10 (the abrasive slurry 1) are recovered as a mixed liquid or as individual liquids. This process is referred to as slurry recovery process A.

  Subsequently, the mixed liquid of the abrasive liquid 4 (the abrasive slurry 2) and the cleaning liquid 10 (the abrasive slurry 1) recovered in the slurry recovery step A, or each of the individual liquids (hereinafter, these liquids are referred to as mother liquids). On the other hand, in particular, an alkaline earth metal salt is added as an inorganic salt without adding a pH adjuster, and only the abrasive is agglomerated and the abrasive is not agglomerated non-abrasive (for example, glass powder). Only the slurry is separated from the mother liquor to concentrate the abrasive slurry (separation concentration step B).

  Next, the solid-liquid separation operation performs solid-liquid separation by natural sedimentation without applying forced separation means. In this way, after separating the mother liquor into a supernatant liquid containing non-abrasive etc. and a concentrate containing recovered abrasive precipitated in the lower part, decantation method, for example, tilting the kettle and draining the supernatant liquid. Or the drainage hype is inserted to near the interface between the supernatant and concentrate in the separated pot, and only the supernatant is discharged out of the pot to recover the abrasive (Abrasive recovery step C). .

  In the present invention, following the abrasive recovery step C, as the step D, it is preferable to perform a particle diameter control treatment of the abrasive particles on the separated abrasive slurry. In the abrasive slurry separated by the above method, the abrasive particles form aggregates (secondary particles) via inorganic salts, so water and a dispersant are added to unravel the state close to the independent primary particles. Then, the particles are dispersed to a desired particle size using a dispersing device (particle size control step D).

  As described above, a high-quality and high-purity recycled abrasive can be obtained by a simple method.

  Next, details of the abrasive recycling method and the construction technique of the present embodiment will be described.

[Abrasive]
In general, abrasives such as optical glass and semiconductor substrates are made by dispersing fine particles such as bengara (αFe ₂ O ₃ ), cerium oxide, aluminum oxide, manganese oxide, zirconium oxide, colloidal silica in water or oil to form a slurry. However, as a polishing material recycling method of the present invention, in order to obtain a sufficient processing speed while maintaining flatness with high precision in the polishing process of the surface of a semiconductor substrate or glass, specific performing polishing on both the activity and chemical action, chemical mechanical polishing diamond applicable capable to (CMP), boron nitride, alumina, recovery of at least one abrasive selected from alumina zirconia and zirconium oxide It is characterized by applying to.

As the abrasive according to the present invention, examples of the diamond-based abrasive include synthetic diamond and natural diamond, and examples of the boron nitride-based abrasive include cubic boron nitride BN (for example, manufactured by Showa Denko KK). Can be mentioned. The boron nitride-based abrasive is an abrasive having hardness next to diamond. Examples of the silicon carbide-based abrasive of the reference example include silicon carbide, green silicon carbide, and black silicon carbide. In addition to alumina, examples of the alumina-based abrasive include brown alumina, white alumina, light red alumina, pulverized alumina, and alumina zirconia-based abrasive. Moreover, as a zirconium oxide, BR series zirconium oxide for abrasive | polishing materials made from a 1st rare element chemical industry company can be mentioned, for example.

  The abrasive used in the present invention is not particularly limited with respect to its components and shape, and those generally marketed as abrasives can be used, and the abrasive content is 50% by mass or more. In some cases, the effect is large and preferable.

[Polishing process]
The abrasive is used in the polishing process as shown in FIG. 1, and the present invention is an abrasive recycling method in which the used abrasive used in such a polishing process is recycled as a recycled abrasive. .

  Taking the polishing of a glass substrate as an example, as explained in FIG. 1, in the polishing process, one polishing process is generally constituted by the preparation of the abrasive slurry, the polishing process, and the cleaning of the polishing part. It is.

(1) Preparation of abrasive slurry An abrasive slurry is prepared by adding and dispersing abrasive powder to a concentration range of 1 to 40 mass% with respect to a solvent such as water. The abrasive slurry is circulated and supplied to the polishing machine as shown in FIG. As the fine particles used as the abrasive, particles having an average particle size of several tens nm to several μm are used.

  By adding a dispersant or the like, it is preferable to prevent agglomeration of abrasive particles and to maintain a dispersed state by constantly stirring using a stirrer or the like. In general, a tank for abrasive slurry is installed next to the polishing machine, and a dispersion state is always maintained using a stirrer etc., and a method of circulating supply to the polishing machine using a supply pump is adopted. Is preferred.

(2) Polishing As shown in FIG. 1, a polishing pad (polishing cloth K) and an object to be polished 3 (for example, a glass substrate) are brought into contact with each other, and an abrasive slurry is supplied to the contact surface. The pad K and the glass substrate 3 are moved relative to each other.

(3) Cleaning A large amount of abrasive is attached to the glass substrate 3 and the polishing machine immediately after being polished. Therefore, as explained in FIG. 1, after polishing, water or the like is supplied instead of the abrasive slurry, and the abrasive adhered to the glass and the polishing machine is cleaned. At this time, the cleaning liquid 10 containing the abrasive is discharged outside the system 9.

With this cleaning operation, a certain amount of abrasive is discharged out of the system, so that the amount of abrasive in the system decreases. In order to compensate for this decrease, a new abrasive slurry is added to the slurry tank T ₁ . The additional method may be added every processing, or may be added every fixed processing, but it is desirable to add an abrasive that is sufficiently dispersed in the solvent.

[Used abrasive slurry]
The spent abrasive slurry in the present invention, there abrasive slurry discharged to the outside of the composed polishing step of polishing machine 1, a slurry tank T ₁ and the washing liquid storage tank T _3, mainly the following two There are types.

The first is the abrasive slurry 1 (rinse slurry) stored in the cleaning liquid storage tank T ₃ containing the cleaning liquid discharged in the cleaning process, and the second is discarded after being used a certain number of times. a slurry tank T ₁ abrasive slurry of spent which is stored in the 2 (life end). Hereinafter, in the present invention, they are referred to as abrasive slurry 1 and abrasive slurry 2, respectively. In addition, although it is preferable to apply this invention to both abrasive slurry 1 and 2, you may apply only to either one.

  The following two points are mentioned as the characteristics of the abrasive slurry 1 containing cleaning water.

  1) Since it is discharged at the time of cleaning, a large amount of cleaning water is mixed, and the abrasive concentration is significantly lower than the slurry in the tank.

  2) The cut glass component adhering to the polishing cloth or the like is also mixed into the abrasive slurry 1 at the time of cleaning.

  On the other hand, a characteristic of the used abrasive slurry 2 is that the glass component concentration is higher than that of a new abrasive slurry.

[Abrasive recycling process]
The abrasive recycling method of the present invention, in which the abrasive is regenerated from the used abrasive slurry and reused as the recycled abrasive, is the slurry recovery step A, separation as described in FIG. It consists of three steps: a concentration step B and an abrasive recovery step C. Furthermore, it is preferable to be composed of four steps in which a particle diameter control step D is added after the abrasive recovery step C.

(1: Slurry recovery step A)
This is a step of recovering abrasive slurry discharged from a system comprising a polishing machine and a slurry tank. The recovered abrasive slurry includes two types of abrasive slurry 1 containing the cleaning water and used abrasive slurry 2.

  The recovered abrasive slurry contains an abrasive in the range of about 0.1 to 40% by mass.

  After each abrasive slurry is recovered, it may proceed immediately to the separation step or may be stored until a certain amount is recovered, but in any case the recovered abrasive slurry is constantly stirred, It is preferable to prevent aggregation of particles and maintain a stable dispersion state.

  In the present invention, after mixing the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A to prepare a mother liquor, the method of processing in the subsequent separation and concentration step B and the recovery step C, Alternatively, the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A may be treated as separate mother liquors in the subsequent separation and concentration step B and the recovery step C, respectively.

(2: Separation and concentration step B)
The recovered used abrasive slurry is in a state in which glass components derived from the object to be polished are mixed. Further, since the concentration is lowered due to the mixing of the washing water, it is necessary to separate the glass component and the like and concentrate the abrasive component in order to use the recovered abrasive again in the polishing process.

  Separation and concentration step B in the present embodiment is performed by adding an alkaline earth metal salt as an inorganic salt to the abrasive slurry (mother liquor) recovered in slurry recovery step A, particularly without adding a pH adjuster. In a state where only the material is aggregated and the non-abrasive material is not aggregated, the abrasive is separated from the mother liquor and concentrated. As a result, only the abrasive component is coagulated and precipitated, and then the glass component is almost present in the supernatant to separate the aggregate, thereby simultaneously separating the abrasive component and the glass component and concentrating the abrasive slurry. It is a process that can.

  A specific operation will be described with reference to FIG.

  FIG. 2 is a schematic view showing an example of the separation and concentration step B and the abrasive recovery step C in the abrasive recycling method of the present invention.

  As the step (B-1), the abrasive slurry (mother liquor) 13 recovered in the slurry recovery step A, which is the previous step, is put into an adjustment kettle 14 equipped with a stirrer 15. Next, in step (B-2), polishing is performed. An alkaline earth metal salt is added as an inorganic salt from the addition vessel 16 to the material slurry (mother liquor) 13 while stirring. Next, in the step (B-3), by adding an inorganic salt, the abrasive particles contained in the abrasive slurry (mother liquor) 13 settle to the bottom to form a concentrate 18. The supernatant liquid 17 from which the abrasive is separated and settled contains a non-abrasive material such as glass, where the abrasive and the non-abrasive material are separated.

<Alkaline earth metal salt>
In the present invention, the inorganic salt used for agglomeration of the abrasive is an alkaline earth metal salt.

  Examples of the alkaline earth metal salt according to the present invention include calcium salts, strontium salts, and barium salts. Furthermore, in the present invention, elements belonging to Group 2 of the periodic table are also broadly defined. , Defined as an alkaline earth metal. Therefore, beryllium salts and magnesium salts also belong to the alkaline earth metal salts referred to in the present invention.

  The alkaline earth metal salt according to the present invention is preferably in the form of a halide, sulfate, carbonate, acetate or the like.

  The alkaline earth metal salt according to the present invention is preferably a magnesium salt.

  Further, the magnesium salt applicable to the present invention is not limited as long as it functions as an electrolyte, but from the viewpoint of high solubility in water, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, Magnesium acetate and the like are preferred, and magnesium chloride and magnesium sulfate are particularly preferred from the viewpoint that the pH change of the solution is small and the settled abrasive and waste liquid can be easily treated.

<Inorganic salt addition method>
Next, a method for adding the inorganic salt to the abrasive slurry (mother liquor) according to the present invention will be described.

a) Concentration of inorganic salt The inorganic salt to be added may be supplied directly to the abrasive slurry (mother liquid) or after being dissolved in a solvent such as water and then added to the abrasive slurry (mother liquid). Although it is good, it is preferable to add in the state dissolved in the solvent so that it may become a uniform state after adding to the abrasive slurry.

  A preferable concentration of the inorganic salt is an aqueous solution having a concentration range of 0.5 to 50% by mass. In order to suppress the pH fluctuation of the system and to make the separation from the glass component more efficient, it is more preferably within a concentration range of 10 to 40% by mass.

b) Addition temperature of inorganic salt The temperature at the time of adding the inorganic salt can be appropriately selected as long as it is not lower than the temperature at which the recovered abrasive slurry is frozen and is in the range up to 90 ° C. From the viewpoint of efficiently performing separation from the above, it is preferably in the range of 10 to 40 ° C, and more preferably in the range of 15 to 35 ° C.

c) Addition rate of inorganic salt The addition rate of the inorganic salt to the abrasive slurry (mother liquor) is uniform as the inorganic salt concentration in the recovered abrasive slurry without locally generating a high concentration region. It is preferable to add such that. The addition amount per minute is preferably 20% by mass or less of the total addition amount, and more preferably 10% by mass or less.

d) pH value at the time of addition In the polishing material regeneration method of the present invention, when adding the inorganic salt in the separation and concentration step B, it is preferable that the pH value of the abrasive slurry recovered in advance is not adjusted. In general, the pH value of the recovered abrasive slurry is slightly alkaline because it contains a glass component, and is in the range of less than 8 to 10. In the present invention, the pH value of the mother liquor in terms of 25 ° C. is 10. It is preferable to perform separation and concentration under a condition of less than 0.

  In the present invention, the pH value is a value measured at 25 ° C. using a Lacom Tester desktop PH meter (pH 1500, manufactured by As One Co., Ltd.).

  In the present invention, it is preferable to add an inorganic salt and then maintain the pH below the pH at the time of adding the inorganic salt until the concentrate is separated. The pH value at the time of inorganic salt addition here means the pH value immediately after the addition of the inorganic salt is completed.

  Therefore, it is preferable to maintain the condition below the pH value at the time of adding the inorganic salt, specifically, the condition of less than 10.0 until the concentrated concentrate is separated.

e) Stirring after addition of inorganic salt After adding the inorganic salt, stirring is preferably continued for at least 10 minutes, more preferably 30 minutes or more. Aggregation of the abrasive particles starts simultaneously with the addition of the inorganic salt, but maintaining the stirring state makes the aggregation state uniform throughout the system, narrowing the particle size distribution of the concentrate, and facilitating subsequent separation.

(3: Abrasive recovery step C)
As shown in FIG. 2, in the separation / concentration step B, the concentrate 18 is recovered after being separated into a supernatant liquid 17 containing a glass component and a concentrate 18 containing recovered abrasive particles.

a) Method for Separating Abrasive Material Concentrate As a method for separating the concentrated abrasive material and the supernatant liquid by adding inorganic salts, a general solid-liquid separation method can be employed. That is, a method of separating only the supernatant by performing natural sedimentation, or a method of forcibly separating using a mechanical method such as a centrifuge can be applied. From the viewpoint of obtaining a high-purity recycled abrasive without mixing impurities (for example, polished glass coarse particles) as much as possible into the concentrate 18 that settles, it is preferable to apply natural sedimentation as the concentration method. .

  Since the recovered abrasive particles aggregate due to the addition of the inorganic salt and are separated from the supernatant in this state, the concentrate 18 has a higher specific gravity than the recovered slurry and is concentrated. . The concentrate 18 contains a recovered abrasive at a concentration equal to or higher than the recovered slurry.

  As an example of a method for separating the aggregate 18 of the aggregated abrasive and the supernatant liquid 17, as shown in the step (B-3) of FIG. 2, the supernatant liquid 17 containing the non-abrasive and the like by natural sedimentation. And the concentrate 18 containing the recovered abrasive precipitated in the lower portion, and then, as shown in step (C-1), the drainage hype 19 is moved to the interface between the supernatant 17 and the concentrate 18 in the pot 14. It inserts to near and only the supernatant liquid 17 is discharged | emitted out of the pot using the pump 20, and the concentrate 18 containing an abrasive | polishing material is collect | recovered.

(4: Particle size control step D)
In the abrasive material recycling method of the present invention, in order to reuse the used abrasive material collected through each of the above steps, as a final step, the abrasive particles aggregated in the secondary particle state are peptized to be primary. The particle size distribution is in a particle state.

  The concentrate collected by agglomerating abrasive particles using an inorganic salt or the like is agglomerated as secondary particles in the state as it is, and in order to reuse, the aggregated abrasive particles are solved, In order to perform a redispersion treatment for obtaining a single particle state (primary particles), it is preferable to incorporate a particle diameter control step D at the end.

  This particle size control step D is a step of adjusting the particle size distribution to be equivalent to that of the abrasive slurry before processing by redispersing the aggregated abrasive components obtained in the abrasive recovery step C.

  As a method for redispersing the aggregated abrasive particles, a) a method of adding water to lower the concentration of inorganic ions in the treatment liquid, and b) an abrasive by adding a metal separating agent (also referred to as a dispersant). There is a method of reducing the concentration of metal ions adhering to c, and c) a method of crushing agglomerated abrasive particles using a disperser or the like.

  These methods may be used alone or in combination, but a method in which any two of a), b) and c) are combined is preferred, and a), b), A method in which all of c) are combined is more preferable.

  When adding water, the addition amount is suitably selected according to the volume of the concentrated slurry, and is generally 5 to 50% by volume, preferably 10 to 40% by volume of the concentrated slurry.

  As the metal separating agent (dispersing agent), a polycarboxylic acid polymer dispersing agent having a carboxy group is preferably exemplified, and in particular, copolymerization of acrylic acid-maleic acid is preferable. Specific examples of the metal separating agent (dispersant) include Polyty A550 (manufactured by Lion Corporation). The addition amount of the metal separating agent (dispersant) is 0.01 to 5% by volume with respect to the concentrated slurry.

  Further, as the disperser, an ultrasonic disperser, a medium stirring mill such as a sand mill or a bead mill can be applied, and it is particularly preferable to use an ultrasonic disperser.

  Examples of the ultrasonic disperser are commercially available from SMT Co., Ltd., Ginsen Co., Ltd., Taitec Co., Ltd., BRANSON, Kinematica Co., Ltd., Nippon Seiki Seisakusho Co., Ltd., and SMT UDU Co., Ltd. 1, UH-600MC, Ginsen GSD600CVP, Nippon Seiki Seisakusho RUS600TCVP, etc. can be used. The frequency of the ultrasonic wave is not particularly limited.

  Examples of the circulation type device that performs mechanical stirring and ultrasonic dispersion simultaneously in parallel include SMT Co., Ltd. UDU-1, UH-600MC, Ginseng Co., Ltd. GSD600RCVP, GSD1200RCVP, Nippon Seiki Seisakusho RUS600TCVP, etc. You can, but you are not limited to this.

  FIG. 3 is a schematic diagram showing an example of a processing flow of the particle diameter control step D using an ultrasonic disperser.

  As shown in FIG. 3, the concentrate 18 prepared by the abrasive recovery work C is added to the adjustment kettle 21, for example, the abrasive dispersion 22 in which the inorganic salt concentration is reduced by adding water to the concentrate. After storing in the preparation vessel 21, a metal separating agent (polymer dispersing agent) is added from the addition container 23 while stirring with the stirrer 15, and then ultrasonic waves are passed through the flow path 24 via the pump 20. Dispersing treatment is performed by the disperser 26 to loosen the agglomerated abrasive particles. Next, the particle size distribution of the abrasive particles after dispersion was monitored with a particle size measuring device 27 provided on the downstream side, and it was confirmed that the particle size distribution of the abrasive dispersion 22 reached a desired condition. Thereafter, the three-way valve 25 is operated, and the abrasive dispersion can be obtained as a recycled abrasive through the flow path 29.

  The particle size distribution obtained in this step is preferably one having little variation with time and little variation in particle size after one day.

[Recycled abrasive]
In the present invention, the final recovered abrasive obtained through the particle size control step D has a small variation with time in the particle size distribution, is higher than the concentration when recovered, and the inorganic salt content is 0.0005. It is preferable that it is the range of -0.08 mass%, and it is preferable that content of another substance is 1.0 mass% or less.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

<Preparation of recycled abrasives>
[Preparation of Recycled Abrasive Material 1]
Recycled abrasive 1 was prepared according to the following manufacturing process. Unless otherwise specified, the abrasive recycling process was basically performed under conditions of 25 ° C. and 55% RH. At this time, the temperature of the solution or the like is also 25 ° C.

1) Slurry recovery process A
In the polishing step shown in FIG. 1, after polishing the glass substrate for hard disk using zirconium oxide as an abrasive, 210 liters of abrasive slurry 1 containing cleaning water and abrasive slurry containing used abrasive 30 liters of No. 2 was recovered to 240 liters as a recovered slurry liquid. This recovered slurry liquid has a specific gravity of 1.03 and contains 8.5 kg of zirconium oxide.

2) Separation and concentration step B
Next, while stirring this recovered slurry solution to such an extent that zirconium oxide does not settle, a 10% by mass aqueous solution of magnesium chloride as an inorganic salt was added over 2.0 liters over 10 minutes. The pH value in terms of 25 ° C. immediately after the addition of magnesium chloride was 8.60.

3) Abrasive recovery process C
After stirring for 30 minutes in the above state, the mixture was allowed to stand for 45 minutes, and the supernatant and concentrate were settled and separated by a natural sedimentation method. After 45 minutes, according to the method described in the step (C-1) in FIG. 2, the supernatant was discharged using a drainage pump, and the concentrate was separated and recovered. The collected concentrate was 60 liters.

4) Particle size control step D (dispersion step)
12 liters of water was added to the separated concentrate. Furthermore, after adding 300 g of Polyty A550 (manufactured by Lion Corporation) as a polymer dispersant (metal separating agent) and stirring for 30 minutes, an ultrasonic disperser (manufactured by BRANSON) was used in the step shown in FIG. Then, the concentrate was dispersed and unraveled.

  After the completion of dispersion, filtration was performed with a 10-micron membrane filter to obtain a regenerated abrasive 1 containing regenerated zirconium oxide. The zirconium oxide concentration was 10.3% by mass, the particle size (D90 <2.0 μm), and the magnesium content was 0.04% by mass.

[Preparation of Recycled Abrasives 2-18]
In the preparation of the recycled abrasive 1, the same type of abrasive as shown in Table 1 and the magnesium chloride used in the dispersion concentration step B to the same mass of inorganic salt as shown in Table 1, And the dispersion apparatus used in the particle diameter control step D was replaced with the dispersion apparatus of Table 1, and the regenerated abrasives 2 to 18 were prepared in the same manner as the preparation of the regenerated abrasive material 1. However, only in the preparation of the regenerated abrasives 4 and 5, the pH value in terms of 25 ° C. of the slurry after the inorganic salt was added in the separation and concentration step B was 10.10, 10 using potassium hydroxide, respectively. .40.

The equipment and materials used are described below.
Bead mill type disperser: Ultra Apex Mill, Kotobuki Kogyo Zirconium Oxide: China HZ Alumina Zirconia: Saint-Gobain Boron Nitride: Showa Denko Alumina: Nihon Micro Coating Co., Ltd.
[Evaluation of purity of recycled abrasive]
About the said reproduction | regeneration abrasive | polishing materials 1-18, according to the following method, component analysis was performed with the ICP emission spectral plasma analyzer, and the purity of the reproduction | regeneration abrasive | polishing material was calculated | required.

  The evaluation is based on the quantitative analysis of the Si content related to the glass component and the specific element attributed to the abrasive, and the total content of the Si content related to the glass component and the specific element attributed to the abrasive. The content of each component was determined.

(Component analysis by ICP emission spectral plasma)
With respect to each of the above-prepared recycled abrasives, the concentrations of the abrasive inherent component and the glass component (Si component) were measured by ICP emission spectral plasma. Specifically, it was performed according to the following procedure.

<Preparation of sample solution A>
(A) 10 g of recycled abrasive was diluted with 90 ml of pure water, and then 1 ml was collected while stirring with a stirrer. (B) 5 ml of hydrofluoric acid for atomic absorption was added (c) Silica was eluted by ultrasonic dispersion (D) Allowed to stand at room temperature for 30 minutes (e) Finished with ultra pure water to a total volume of 50 ml Each specimen solution prepared according to the above procedure is referred to as sample solution A.

<Quantitative determination of Si>
(A) Sample solution A was filtered with a membrane filter (hydrophilic PTFE). (B) The filtrate was measured with an inductively coupled plasma emission spectrometer (ICP-AES). (C) Si was quantified by a standard addition method.

<Quantification of abrasive specific elements>
(A) Sample solution A was well dispersed and 5 ml was collected. (B) 5 ml of high-purity sulfuric acid was added and dissolved. (C) Finished to 50 ml with ultrapure water. (D) ICP- Measured by AES (e) Each abrasive specific element was quantified by a matrix matching calibration curve method.

<ICP emission spectral plasma device>
ICP-AES manufactured by SII Nano Technology was used.

  Table 1 shows the analysis results obtained as described above.

  As is clear from the results shown in Table 1, the abrasive recycling method of the present invention is higher in purity of the resulting recycled abrasive material than the comparative abrasive recycling method, and efficiently removes glass components that are impurities. You can see that.

Example 2
In the preparation of recycled abrasives 1 to 7 using zirconium oxide as the abrasive described in Example 1, the abrasive was replaced with zirconium oxide, and synthetic diamond (manufactured by Nippon Micro Coating Co., Ltd.) and silicon carbide ( as a reference example ) Recycled abrasives 101 to 107 (synthetic diamond) and recycled abrasives 108 to 114 (silicon carbide) were prepared in the same manner except that Nippon Micro Coating Co., Ltd. was used.

Then, for each reproduction abrasive material obtained, similar measurement the result of, even with synthetic Diamon de as an abrasive, it can be confirmed that it is possible to obtain the same results and zirconium oxide.

  By the abrasive material recycling method of the present invention, the abrasive material can be recovered from the used abrasive slurry by an efficient method, and then a high-purity recycled abrasive material can be obtained by a simple method.

DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Polishing surface plate 3 Object to be polished 4 Abrasive material liquid 5 Slurry nozzle 7 Washing water 8 Washing water jet nozzle 10 Cleaning liquid containing abrasive 13 Abrasive material slurry (mother liquid)
14, 21 Adjustment pot 15 Stirrer 16 Addition vessel 17 Supernatant liquid 18 Concentrate 19 Drainage hypo 20 Pump 25 Three-way valve 26 Ultrasonic disperser 27 Particle size measuring device A Slurry recovery process A
B Separation and concentration process B
C Abrasive recovery process C
D Particle size control process D
E Inorganic salt F Recycled abrasive material K Polishing cloth N Pressing force T ₁ Slurry tank T ₂ Washing water storage tank T ₃ Cleaning liquid storage tank

Claims (11)

A polishing material regeneration method for regenerating an abrasive contained in the abrasive slurry from a used abrasive slurry, wherein the abrasive is at least one abrasive selected from the following abrasive group, and A method for regenerating an abrasive material comprising regenerating the abrasive material through steps A to C.
Step A: Slurry recovery step A for recovering the abrasive slurry discharged from the polishing machine.
Step B: To the recovered abrasive slurry , an alkaline earth metal salt is added as an inorganic salt in a state in which no pH adjusting agent is added and a non-abrasive is not aggregated to aggregate the abrasive, and the abrasive Separation and concentration step B, in which the product is separated from the mother liquor and concentrated.
Step C: Abrasive recovery step C for recovering the separated and concentrated abrasive.
Abrasive group: diamond, boron nitride, Alumina, alumina zirconia and zirconium oxide.   2. The abrasive recycling method according to claim 1, further comprising a particle diameter control process D (process D) for adjusting a particle diameter of the recovered abrasive after the abrasive recovery process C. 3.   The method for regenerating an abrasive according to claim 1 or 2, wherein the separation and concentration step B performs separation and concentration under a condition that the pH value of the mother liquor in terms of 25 ° C is less than 10.0.   The said slurry collection | recovery process A collect | recovers the abrasive slurry 1 and the used abrasive slurry 2 containing washing water, The abrasive | polishing material as described in any one of Claim 1 to 3 characterized by the above-mentioned. Playback method.   5. The abrasive recycling method according to claim 4, wherein the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A are mixed and then processed in the separation and concentration step B and the recovery step C. 6. .   5. The abrasive recycling according to claim 4, wherein the abrasive slurry 1 and the abrasive slurry 2 recovered in the slurry recovery step A are independently processed in the separation and concentration step B and the recovery step C, respectively. Method.   The method for regenerating an abrasive according to any one of claims 1 to 6, wherein the alkaline earth metal salt used in the separation and concentration step B is a magnesium salt.   The method for recovering an abrasive material according to any one of claims 1 to 7, wherein the method for recovering the abrasive material in the abrasive material recovery step C is a decantation separation method by natural sedimentation.   In the particle size control step D, after adding a dispersant to the recovered abrasive solution, the particle size of the recycled abrasive is controlled by dispersing using an ultrasonic disperser or a bead mill type disperser. The method for reclaiming abrasives according to claim 2.   The method for regenerating an abrasive material according to claim 9, wherein the disperser used in the particle diameter control step D is an ultrasonic disperser.   The method for regenerating an abrasive according to claim 9 or 10, wherein the dispersant is a polycarboxylic acid polymer dispersant.

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